Factor analysis of the St. Mary's Hospital Sleep Questionnaire.

The St. Mary's Hospital Sleep Questionnaire was designed to evaluate the sleep of hospital patients. To gain an understanding of possible underlying factors, the questionnaire was factor analysed using data collected from 222 hospitalised rheumatic patients. The analysis did not produce a completely clear factor structure. Two factors relating to "sleep latency" and "sleep quality" emerged more clearly than the other factors produced. These factors correspond with two sleeping state factors (ease of getting to sleep; quality of sleep) that were extracted by a previous factor analysis of the Leeds Sleep Evaluation Questionnaire. This suggests that the two most important aspects of subjectively perceived sleep are the process of going to sleep and the quality of sleep.